The invention is in the art of power operated hydraulic fluid and grease dispensers, and in particular to a grease gun having a reciprocating plunger driven with a power unit to pump grease into a grease dispenser.
Grease guns having reciprocating plungers operated with power units, such as pistons drive by air and hydraulic fluid pressure or electric motors, to pump grease through a grease dispenser, such as a tube and fitting are common use. These grease guns have tubular members releasably connected to the bases of the guns that accommodate cartridges containing grease which is forced into pumping changers. Reciprocating plungers are moved with power units relative to the pumping chambers to force grease through the passages and check valves into the tubes and fittings. When air is trapped in the pumping chambers, plungers do not pump grease. Air bleed valves on the bases of the grease guns are used to bleed air from the tubular members to eliminate an air lock in the upper ends of the tubular members. These air bleed valves do not bleed air from the pumping chambers and thus do not solve the problem of removing air trapped in the pumping chambers and allow grease to flow into the pumping chamber. E. H. Scovell in U.S. Pat. No. 2,505,839 describes an air operated grease gun having a plunger 1 that reciprocates in a pumping chamber to move grease past a check valve 21 through a nozzle 23. A screw type air valve 24 located on nozzle 23 downstream from the check valve 21 is used to allow air to be bled from the nozzle. The check valve 21 prevents air from flowing out of the pumping chamber and does not solve the problem of bleeding air from the pumping chamber.
The invention related to an air operated grease gun having an air bleed valve operable to allow air to bleed from the pumping chamber of the grease gun enabling a reciprocating plunger to pump grease. The air bleed valve prevents air lock in the pumping chamber between a check valve and the grease pumping chamber that accommodates the plunger. The air bleed valve is an effective low-cost one-piece member that overcomes the air lock problem of power operated grease guns.
The grease gun has a body having a cylindrical pumping chamber and a grease supply passage intersecting the chamber. A power unit mounted on the body has a plunger that reciprocates in the pumping chamber to pump grease through the pumping chamber and a check valve into a grease dispenser. An air bleed valve aligned with the grease supply passage is manually operable to open the air bleed valve to allow air to flow out of the pumping chamber, passage and grease contain er retained on the body with a tube. The air bleed valve has a threaded stem located in a threaded hole in the body. At least one linear groove in the side of stem allows air to bleed out of pumping chamber when the valve is turned to the open position. Grease replaces air in the pumping chamber and the passage so that the plunger reciprocates in pumping chamber to pump grease through the pumping chamber. A head on the stem engages the body when the stem is turned down to the closed position. The stem does not extend into the pumping chamber. An alternative air bleed valve has a threaded stem turned into a threaded bore in the body in axial alignment with the passage open to the pumping chamber. The stem has a plurality of linear grooves extending about one-half the length of the stem. An annular seat assembly surrounding stem below as head on the stem is held in sealing engagement with the body. The seal assembly has an O-ring and washer with outwardly directed fingers that inhibit rotation of the O-ring during opening and closing of the air bleed valve. When the stem is turned to the open position linear side grooves are open to atmosphere thereby allowing air to bleed from the pumping chamber to atmosphere. Grease replaces the air in the pumping chamber. When the air is bled from the pumping chamber, the stem is turned down to close the air bleed valve thereby preventing grease from flowing through the air bleed valve and air from flowing into the pumping chamber. Operation of the power unit reciprocates the plunger which pumps grease through the pumping chamber past the check valve into the grease dispenser.